Light-transforming compositions.



PETER COOlPER HEWITT, OF RING-WOOD MANOR, NEW JERSEY, ASSIGNOR TO COOPERHEWITT ELECTRIC COMPANY, OF HOBOKEN, NEW JERSEY, A CORPORATION OF NEW JERSEY.

LIGHT-TRAN SFORMIN G COMPOSITIONS.

Specification of Letters Patent.

Patented June 27, 11918.

.No Drawing. Original application filed July 23, 1910, Serial No.573,557. Divided and this application filed October 20, 1913. Serial No.796,170.

My invention relates to the class of devices employed for combining raysof a source of light which is deficient in some desired portion of thespectrum with rays of other wave length produced by the transformationof certain rays or waves of one I length into rays or waves of anotherlength and of such character as to supply the ray or wave lengthdesired, Within limits.

In a patent issued to me on December 22,

1908, bearing N 0. 907,598 and in a companion application Serial No.453,187, filed by me September 15, 1908, I have described certainmethods of producing and utilizing light rays of the character referredto, and my present invention relates more particularly to specialcompounds of materials to be used for transforming light rays and, whendesired, adding light waves of definite character to light from anysource.

Retentiveness of the fluorescent quality, or durability of the propertyof transforming light, seems from experiment to be seriously modified bythe internal structure or physical arrangement of the material its finalstate: that is, the material retains this light transforming propertybetter and for a longer period by reason of its being or having been ina state of internal stress or by reason of the fact that the internalstructure is fibrous in nature. It is impor-' tant also that theconditions of drying or hardening of the material be properly carriedout,.as affecting the physical relation of the materials to each otherduring manufacturing and as afl'ecting the finished product.

In practice I find that, while several dif-' ferent materials andcompounds may be used with greater or less efliciency and durability orretentiveness, most excellent results are obtained by the use ofrhodamin combined in proper proportions with acetate of cellulose towhich glycerin has been added. A combination or "association of parentmerce as cellet may be used and prepared as follows:

It may be first bleached with permanganate of potash made acid withsulfuric,

acid, and subsequently treated with sulfurous acid for further bleachingand removing the permanganate, and washed with water until free fromsalts. An amount vof rhodamin, equivalent to three one-hundredths byweight of the Weight of cellet and glycerin is added, the rhodamin beingin solution in alcohol or acetone for convenience. The whole forms avarnish which when dry may be used either for reflecting purposes or asa light screen or filter, that is to say, it may be painted upon asuitable backing and when dry the transformed light reflected therefromand mingled with the light from the source, or it may be made into afilm or painted upon a proper transand placed wholly orpartially'arouiide dthe source of light so that -more or less of theoriginal light and the transformed light will be mingled.

In an application filed by me September 18, 1909, Serial Number 518,325,I have described various forms of backings or supports for varnishes ofthis general character and also materials which may be mixed with thevarnish for the purpose of increasing the light qualities thereof. Whenit is to be placed upon a backing or support to serve as a lightreflector, I have found it advantageous to use as the immediate supportfor the varnish a material, such for instance, as calcimine of whitelead, or other material having the characteristics -of dispersing light.11 some instances it may be desired to mix the light-dispersing materiala with the varnish. r

. The proportions above given may be modified to a reasonable degree,but those given above are found to produce a material having efiicicncyand durability combined.

In the drying of the material, the acetic acid and acetone evaporate,leaving the acetate of cellulose, color (such as rhodamin), and anamount of glycerin as the light transformer.

The varnish may be painted upon a suitable temporary support and driedand then stripped oil from the support and used independently-of anyother support as the light reflector or screen.

Any desired number of coatings of the varnish may be painted upon thesupport in succession. I have found, for instance, that five coatsquickly flowed, one after the other, gives a very eflicient result.

This application is a division of my a plication Serial Number 573,557,filed J y 23rd, 1910.

I claim as my invention:

A composition for forming a light transformer consisting, substantiallyin the proportions described, of acetate of cellulose, a fluorescentdye-stufi and a volatile solvent therefor, glycerin, and acetic acidsuflicient to modify the structure of the acetate of 1 cellulose ondrying.

Signed at New York in the county of New York and State of New York this16th day of October A. D. 1913.

PETER COOPER HEWITT. Witnesses:

WM. H. CAPEL, THOS. H. BROWN.

